Bill Fitzmaurice

You don't have 21L per driver as the port and drivers take up volume. You'd model it in your case with 4 drivers. A pair of 10cm ID ports would give acceptable port velocity. With a 70L net cab volume they'd be 20cm deep. You have to figure out what volume they occupy, plus a liter each for the drivers, to find the remaining net box volume. Then you'd do any further adjustment of that box volume in the model to see any required lengthening or shortening of the ports. Don't sweat getting it all perfect, a tolerance of 5% or so in either direction is OK.

No doubt it's too large to provide a low enough tuning to work well with bass, but again at gig levels. Even open back, a misnomer as they're not totally open, can sound good in the studio, they just lack the output for gigging. The '59 Bassman for instance, or one of Carol Kaye's preferred studio amps, the Fender Concert, with reverb, which she often used. You can hear it on many of her Beach Boys tracks.

That depends on the 210 and the 115. But mixing a 210 with a 115/6 opens up more cans of worms best left undisturbed.

This is what's possible with an eight that's well suited for electric bass, in this case the B&C 8BG51, in 18 liters net, ported, tuned to 50Hz:

All porting used to look like that, being a hole cut in the baffle, or as in this case in the back, with no duct. The common use of ducts dates to circa 1965, more or less coming into use at the same time as Theile/Small specs. What's usually referred to today as a port is more properly called a ducted port.

+1, and the pertinence goes back to where the OP stated his reasoning behind wanting to add a 115 to a 210 is to get better lows. That assumption isn't supported by the facts.

It's considerably better than the Celestion, which should never have been loaded in a sealed cab for bass to begin with, but still limited in low frequency capability. I wouldn't consider anything with a higher than 60Hz Fs, and of course the rest of the specs would have to work in the intended enclosure.

You don't have to know what it means, so long as I know what it means. 😎 In layman's terms that speaker probably can't go either low or loud enough for gigging at more than what we refer to as coffee house levels on my side of the pond. I'd say it's much better suited to low level studio work than gigging.

Obviously one would not expect a five to equal the output of an eighteen, but a grouping of fives would. What determines a drivers low frequency response is the Theile/Small specs. Cone area (Sd) is only one of some fourteen T/S specs, and of those specs Sd has no influence on how low a driver can go. That is primarily the result of the driver Fs, Vas and Qts.

That's probably not going to cut it, not because it's 'only' 100 watts, but because the speaker is not well suited for bass. The cabinet is too small, and the port configuration shows that it's tuned much too high.

Beware of what 'we all know', as it's as likely as not incorrect. One can find, without too much searching, a five and an eighteen that go equally low. Where the five would come up short is in maximum output. A 115 may give better lows than a 210, it may not. My advice in this respect is always the same: if you don't like the sound of your speaker get one that you do like the sound of. If one isn't loud enough get two.

A few notes: Sealed enclosures have better transient response Transient response is a primarily a factor in the higher frequencies, where the cabinet alignment has no effect. A very poorly designed ported enclosure can have poor transient response in the mid bass, but being very poorly designed it will have other problems as well. A well designed ported enclosure will not have any transient response issues. This is one reason why they sound punchier and more accurate. In blind testing with the systems EQ'd for identical response listeners are unable to identify ported versus sealed cabs. There is no difference in accuracy so long as the speakers are not played at a high enough level for there to be high level harmonic distortion. 'Punch', by and large is the term applied to the sound of a speaker being pushed past its linear excursion limits, resulting in high level harmonic distortion. High THD isn't more accurate, it's less accurate, and it's far easier to realize with a sealed cab than ported. It's also neither inherently good nor bad where amplified instruments are concerned, being a matter of taste. If you have a ported cab and want to get it to sound like sealed that's easy enough, turn the bass EQ down. If you have a sealed cab and want it to sound like ported turn the bass EQ up. The ported cab with lower bass EQ still won't have the THD of sealed, and the sealed cab with bass EQ boosted still won't have the low end output capability of ported, but that's why you can still buy both types. There are some disadvantages to ported enclosures. Transient response is poor compared to a sealed enclosure. The result is decreased accuracy. If ported enclosures had less accuracy than sealed then the vast majority of high end speakers, as in over $10K each, would be sealed. They're not. For that matter the vast majority of speakers are ported, irrespective of the price range. A poorly designed ported enclosure can cause all sorts of problems. That's true, but since the advent of speaker modeling software back in the 1990s there's no excuse for a ported enclosure to be poorly designed, other than the designers lack of knowledge. There is one instance where by and large a sealed enclosure is preferable to ported, that being a mid bass speaker specifically intended for use with a subwoofer. When a speaker isn't going to be used below 80 to 100Hz in most cases sealed will work just as well as ported, so there's no good reason to incur the added design complexity, cost and physical size of a ported enclosure.

Speakers don't deliver watts, and Hoffman's Iron Law is immutable. That doesn't necessarily mean it's not a decent enough piece of kit, but I'd have to see some real data before making any assumptions about how well it compares to the competition.

Or a 30 watt Ampeg B15, depending on the gig.

Amused we are not.

Don't be so sure about that. Most rehearsal spaces are small enough that you'll get a lot of boundary sourced phase cancellations, which can make your amp sound not as loud as it will in a large room. Guitars and drums don't have this issue, as the wavelengths they produce are much shorter and are relatively immune to phase cancellations.

If you have an NLF2 connector there's no choice on how to wire it, there being only 1+ and 1- poles. It's only with the NLF4 connector that you have 1+,1-, 2+ and 2- poles.

Make your own. I can't imagine anything more easy than making Speakon cables. You will want to use colored adhesive tape, paint or some other method of identifying the amp connection versus the speaker connection.

You'd probably find a bass though any speaker with no type of frequency shaping lacking. Even bass amps that supposedly have flat response when the tone/EQ knobs are set to noon still tend to have a pretty fair amount of pre-shape EQ.

Makes one wonder how James Jamerson ever got by with just a Fender bass, Ampeg B15 and a cord. 🙄

I've used the same bass for 20 odd years, don't quite understand the need for more than one. Whatever tone changes I make from song to song I do with my hands.

The EQ has the same effect either way. A decibel is a decibel.

That's OK if you want the cleanest sound possible. You'd do the opposite for the dirtiest sound possible.

Running higher gain with lower volume gives less clean headroom, for a dirtier sound. Running lower gain with higher volume gives a cleaner sound. As for active versus passive, active has higher output, so it tends to clip more easily when played through the passive input. All the active input does is to lower the input gain, also giving more headroom and cleaner tone.

When you add a second cab to your rig to provide more power handling and output where that power handling and output is required isn't above 120Hz, it's below 120Hz, so I question the value of what you propose. I wouldn't use the SM110 in a sealed cab, partly because its specs aren't well suited for sealed, partly because it won't have enough low end even as a rehearsal cab. I'd put it in a 40 L (net) VB with 50Hz tuning to get out of that driver what it has to give. It's still not like it will be a huge cab by any means. Then if it adds worthwhile output used along with one of your other cabs all well and good. If not at least you have a decent rehearsal cab. As for high passing at 120Hz, to have a useful result you'd need at least second order filtering, which is impractical and expensive with a passive.